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World’s tiniest snail is so small that 10 fit in a needle’s eye

By Aisling Irwin

A microsnail, indeed(Image: Barna Páll-Gergely)

It’s the ultimate downshifter, opting to be tiny in the quest for a quiet life. Angustopila dominikae is a microsnail – a snail less than 5 millimetres in length – and could be the smallest land snail ever recorded: 10 would fit in the eye of a needle.

A single specimen was found among soil samples gathered in 2013 by András Hunyadi, a Hungarian traveller and shell collector. So far seven new microsnail species have turned up in these samples, taken at the foot of a limestone hill in Guangxi province, southern China.

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A. dominikae is the smallest of these. At just 0.86 millimetres in height, it is 9 million times smaller, by volume, than its biggest relatives – some of the giant African land snails, says Ben Rowson of the National Museum of Wales in Cardiff, UK.

Being tiny means it can live in minute crevices in steep limestone peaks, says Barna Páll-Gergely of Shinshu University, Japan, who led the team that identified it. There, it probably lingers within its plain grey shell until it rains, when it comes out to graze on algal films that grow in moist conditions.

Tininess may also help protect it, although no one knows for sure. “The problem living in the tropics and subtropics is that there’s an army of micro-arthropods that dearly like to eat snails,” says Richard Preece of the University of Cambridge’s Museum of Zoology. While other snails have evolved defences in their shells such as tooth-encrusted apertures, trap doors or safe rooms, A. dominikae seems to have gone for keeping a low profile instead.

Single shell

There is only a single shell of A. dominikae to go on and no traces of DNA, so many unanswered questions remain about its lifestyle, says Páll-Gergely.

But other microsnails are known to live on limestone mountains rising above the forests of China, Thailand and Malaysia. They may have suffered from competition for resources in these isolated habitats, which might have driven down their size, Preece says.

Could there be even smaller microsnails awaiting discovery? Some researchers think it’s possible, and that such creatures may have dispensed with an organ such as the lung in the quest to miniaturise themselves. Others, including Rowson, think not. “You can’t be much smaller if you want to be a complicated animal,” he says. “And snails are pretty complex.”

Besides, he thinks that a tinier snail might dry out, partly through exuding slime to aid movement. “The leading cause of death in snails is thought to be desiccation. If you are that small, it’s hard to avoid it,” he says.